I followed this recipe. It follows the pattern outlined here but with different temps:

Get milk. – I’m using 1 cup of 2% (no powdered milk).

Get a starter. – I have tried Dannon Oikos plain greek yogurt (made with whole milk), and Yoplait Very Vanilla, and some other brand of plain greek yogurt. The “other brand” yogurt was at least a couple weeks in the fridge before I tried using it for starter.

Heat the milk to 175-180°F ( instead of 190°F).

Cool the milk at to between 40°C (110-120°F).

Mix in the starter. (I used ¼ tsp for 1 c milk.)

Keep the mix warm for 6-10 hours. – For the heat source I used a crock pot on “keep warm” with 2-3” water. The milk/starter was loosely covered in a class measuring cup. I monitored the temp with a thermometer and kept it around 110°F. (It probably varied from say 105-115° as I tried to keep the temp 110°)

Strain your yogurt. – The one batch that solidified, I successfully strained with a coffee filter. My problem is just getting to this point.

The first time I made it, I heated my oven to 170°F (as low as it goes) and then turned it off. I wrapped the still warm milk/starter (in a glass bowl) in towels in an oven that had been heated to 170°F and then turned off. I used the “Very Vanilla” starter and in the morning it was still milk, so I added some plain greek yogurt and transferred it to a crock pot on keep warm, with the crock pot lid on and a towel over the lid. After several more hours it had solidified but was beige colored. At that point, a temp check revealed it was 170°F. Oops. After straining it, the texture resembled ricotta cheese. It smelled nutty and delicious, but didn’t taste nutty or delicious. I think it was getting all that smell from the whey. The taste was not unpleasant, but not pleasant either, and definitely not tart like yogurt.

The second/third times I made it, I just used plain greek yogurt starter. Incubated in a crock pot with a water batch for 8-10 hours. The result was milk. When I poured out the milk I could see some solids (what looked like the starter) at the bottom.

So now I’m wondering what went wrong. Several questions come to mind:

Is my starter too old? If so, how do I get fresh yogurt?

Am I using enough starter?

Am I getting the milk hot enough in step 3?

Am I keeping the milk too hot/cold during incubation?

Does the humidity from the water bath help/hurt my chances of producing yogurt?

Can anyone offer some guidance? I have a hunch that the starter is too old since I don’t really know how old yogurt is when I buy it from the store. But I also don’t know how to do any better than buying it from the store and making yogurt right away.

There are so many variables I’m not sure of that I just thought it would be good to get some advice before proceeding.

5 Answers
5

Don't get frustrated. There really aren't that many variables to keep track of.

1- I don't know the age of store bought yogurt but I have never had just-purchased yogurt not work as a starter. I have had month old yogurt from my fridge not turn out. If you don't plan on making yogurt often enough to keep you starter viable then consider freezing some in ice cube trays.

Whatever starter you use- make sure it lists "live, active cultures". Personally I wouldn't use a flavored yogurt as a starter.

2- I don't think that is enough starter. I will use 1/4 cup of starter for a quart of milk. If you are using 1 cup of milk that would be one Tbs of starter (12X the amount you used).

3- It depends. The goal is to denature the albumin proteins in the milk. 180F is hot enough if the milk is held at that temperature for at least half an hour. It needs to be held at 190F for closer to 10 minutes.

4- You need to get better control of your temperature. 130F will kill your starter but erratic temperature fluctuations will also produce very poor yogurt. Without a temperature controller or manual intervention your slow cooker will get much too hot- even with a water bath.

More successful approaches are to put it in a draft free place in an insulated container, or in your switched off oven.

5- The humidity is not going to play a role unless it is condensing into your container enough to dilute things.

Thanks I'll give this a try tonight. Maybe I'll use the oven instead of the crock pot. It would work better for large quantities anyway.
– StainsorOct 2 '12 at 14:39

3

It worked!! I'm so pumped, I finally made edible yogurt! It wasn't GOOD yogurt, but it was definitely yogurt. I have to credit the increased amount of starter. ... I preheated my oven to 170 with a baking stone while I was brining my milk up to 190. Then I switched off the oven and put the 190 degree milk in for 10 minutes. I took it out for about 15 minutes to cool before adding the starter (Dannon Oikos) and then back in the oven. Eight hours later I had yogurt! It definitely needed more time to increase the tartness. But now I've got something to build off of. Thanks!
– StainsorOct 4 '12 at 13:13

1

I have now realized that I was overheating my yogurt. I don't preheat my oven to 170 anymore, I just turn on the oven light. I get a much smoother yogurt now. Especially when I skim off the rough top layer. By morning it is around 125 degrees. So I am thinking that the (40 Watt) oven light alone may provide too much heat. I'm going to try keeping the oven door part way open. I may even try turning off the oven light (with the door closed).
– StainsorJan 18 '13 at 19:00

I see that you have had success with the answer above, so congrats. I have been using these general guidelines for making yogourt and it's turned out nicely except for once (and only because I needed the oven half way through making the yogourt - poor planning on my part!):

2L of 3.8% organic milk (full-fat happens to be my preference because I prefer the taste)

I initially used plain organic Greek yogourt as a starter, 4 tbsp. for the 2L of milk

Heat milk to 180F and hold at that temp for 30 mins.

Cool down to 110F (I use a quick cool function in my fridge)

Add the starter and mix gently (I use a silicone spatula - I read several recipes that emphasize the 'gently' part; I think it has to do with not breaking apart the molecules)

Place in oven with light on and leave for 8-10 hours or until desired acidity is reached.

I use a dutch oven to make the yogourt and I always use a thermometer.
I keep a small mason jar of the yogourt as a starter for next time and have occasionally kept it for two weeks between batches with no ill effects.

I then strain the yogourt in a cheesecloth-lined mesh colander in the fridge for 4-6 hours or until I have my preferred consistency of thick Greek-style yogourt. The final yield is about a litre and costs about half of what I would pay for organic Greek yogourt in my part of the world - and the taste is far superior in my opinion.

Maybe if your oven looks like it won't go that low, try to see if it will stay on if you move the knob below the temperature markings. I found although mine said it could only go to 60 degrees Celsius (140 F) it actually will go lower and maintain the right temp to make the yoghurt. Just a thought :-)

If you find following a detailed recipe too error-prone, start simpler instead. Make your earliest efforts as simple as possible, and start small. Your first successes can come by following this simplified recipe:

(1) Warm the milk to 110 degrees Fahrenheit.

(2) Add yogurt.

(3) Keep the mixture in a warm but not hot place for 6-8 hours.

Yogurt should grow as long as it has food (lactose) and is warm and is not being out-competed by another microbe colony. Cultures can die, and simply trying again with fresh yogurt or working on keeping the temperature in a more comfortable range for the cultures can lead to an earlier success. Some steps may be extraneous for your first experiments, but add them back in after you start to see some moderate success (as another writer pointed out, pre-heating the milk helps the yogurt thicken more). Probably the most difficult part is maintaining the temperature within the cultures' optimal growth range; 100-120 is typically OK, but colder leads to slow/no growth and hotter can kill the cultures, making a fresh cheese instead of a yogurt. Most cooking appliances are not designed to operate within this temperature range and that is the chief difficulty--ovens and crockpots usually don't go below about 140 or 170 F--so many people will put it in a turned-off oven with residual heat, and with the oven light on or with tins full of hot water next to it (120-140F) to keep it warm. A friend of mine would pour some milk on top of the last spoonful in her yogurt cup and leave it next to the warm fan vent of a computer. She'd come back in the morning and she'd have another cup of yogurt waiting for her.

After stirring in the live culture yogurt, I let it set for 11 hours overnight in the oven with the light on (Crockpot wrapped in a large beach towel). Stirred it again in the morning.
My cousin leaves hers setting out longer covered with cheesecloth which results in a thicker yogurt.

I made a second batch today using 1 cup of the first batch of yogurt. We'll see how that turns out in the morning.

Hi Celeste and welcome to Seasoned Advice. Although I only skimmed the recipe you posted, the key differences between this and those described in the question don't jump out at me. Maybe you could point out what you think is important.
– Chris SteinbachJan 13 '13 at 6:25